Sound projector



Dec 18, 1923. 4 r

E. GRISSINGER SOUND PROJECTOR Origl 3 Sheets-Sheet l Ms A TTORNEY Dec. 18, 1923. 1,477,554.

E. GRISSINGER SOUND PROJECTOR Original Filed June 20, 1919 I5 SheetsSheet 2 /NVE/VTOR H/S'ATTORNEY Dec. 18 1923.

E. GRISSINGER SOUND PROJECTOR 3 Sheets-Sheet 5 Original Filed June 20 1919 HIS'ATTORIVEY Patented Dec. 18, 1923.

UNITED STATES 1,417,554 PATENT OFFICE,

ELWOOD GRISSINGER, OF BUFFALO, NEW YORK, ASSIGNOR TO LUCY ASH GRISSINGER, 0F BUFFALO, NEW YORK.

SOUND PROJECTOR,

Application filed June 20, 1919, Serial T 0 all whom it may concern:

Be it known that l, Enwooo Gmssmonn, a citizen of the United States, and resident of Buifalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Sound Projectors, of which the following is a specification.

My present invention relates to sound pr0 jectors of the type used for transferring to the outer air sound waves propagated through a guide tube or conduit of relatively small cross-section, as, for instance, the tone arm of a phonograph. it relates more particularly to projectors wherein the sound waves from the guide tube are advanced between expanding walls of the projector by successive reflections from thin sonorous plates or sounding boards. Pro jectors of this type are disclosed in my prior application Serial No. 298,846 filed May 22nd, 1919. As explained more fully in said application, the angles of impingement of the waves upon the successive reflectors is high enough so that the impinging waves will be effective in causing consonant vibration of the sonorous plate reflectors, without having them so high that the reflected waves will be thrown back toward the sourceinstead of toward the open end or the projector.

As further pointed out in said application, the sonorous plates set in vibration by the impinging waves each become sources of additional sets of sound waves radiated perpendicularly therefrom. These sets of re-radiated waves are very important factors and their lines of propagation and reflection are governed so that they, too, will be advanced through the projector and emitted from the mouth thereof along with the primary reflected waves.

In my prior application three sonorous reflectors were employed in such relation that the primary reflection, that is, the main beam, and the re-radiation from the first reflector, and the re-radiation from the upper half of the third reflector all had direct lines 01": propagation through the projector and substantially free emission from the open end thereof. Such emission was at Widely divergent angles, however, and the second and third reflectors being parallel and overlapping, the re-radiation from the second reflector and from half of the first No. 305,601. Renewed March 6,1923.

was lost except as to such part as could escape by lateral diffusion.

The object of my invention is to provide an arrangement of sonorous reflectors whereby much more of the re-radiationwill be emitted; and whereby the several sets of rc-radiated waves will be emitted as nearly parallel with each other, and with the primary or main beam waves, as may be desired.

The essentials for securing these results will be more fully understood from the following description in connection with the accompanyingdrawings, in which Figure l is a diagrammatic view indicating a longitudinal section through the projector, and the tube which guides the primary sound waves thereto, the theoretical path of the several sets or" waves being indicated by arrowed lines;

Figures 2 and 3 are similar views of modifications.

The details for structural support of the projector and of the phonograph or other source oi sound to be projected, may be oi any known or desired form, but preferably the projector is embodied in a phonograph cabinet after the manner of the projector shown in my above mentioned prior application.

Reterring to'l igure i, it will be seen that a pipe 11 which may connect with the tone arm of the phonograph guides the sound waves downward from point a. From the lower end of said pipe, they are projected downward on reflector 12 arranged at an angle of 45 degrees. This reflects the waves impinging at b, b horizontally so that they impinge on reflector 13 at c, c. Reflector 13 is at an angle of 67%,; degrees to the horizontal-so that it reflects the waves at an upward angle of 45 degrees to vertical reflector 14, whence they are reflected from points (i, (Z at an angle of 45 degrees in the reverse direction to impinge upon reflector 17 at e, e. Reflector 17 is at an angle of 22% degrees to the horizontal and consequently the main beam is again reflected horizontally from e, 6 through the mouth of the projector along horizontal lines f, f.

In the particular case shown in the drawings, reflectors 12 and 14; are thin sonorous plates or sound boards adapted to be set in' vibration by energy of the waves impinging till? thereon and consequently they are each a source of a separate set of sound waves rera'diated perpendicularly from the surface of each.

The set of waves from reflector 12 are reradiated from points 9', g perpendicularly 'to the surface thereof at an angle of 4:5 degrees above horizontal, so that, impinging upon reflector 17 at it, they are reflected to 2', 11 horizontally .and therefore parallel with the main reflection previously described.

Plate 1t being vertical, the re-radiation from points m, m along lines n, n is initially horizontal without being reflected.

lit will thus be seen that these three sets of Waves are emitted parallel with each other and that the re-radiated Waves have particularly directed paths of emission.

The re-radiation from 13 is partly reflected backward and lost, although a considerable fraction of it is reflected from 14% in a fairly good general direction with the rest of the emitted waves.

As explained in my prior application, the amount of energy absorbed and re-radiated by the sensitive sonorousreflectors will be greater when the plates are very thin and thereforeflexible as well as highly elastic and sonorous. Consequently, the proportion ot the primary energy of the main beam that will be finally emitted as compared with that which will be absorbed by the successive reflectors may be predeter-' mined and adjusted by making the reflectors as thin and flexible as consistent with good resilience and sonorous vibratory quality. Then the energy absorbing and re-radiating qualities being a maximum, may be de creased as much as desired by providing ten= sioning wires 20, preferably piano wires, secured to one frame member 21,.deflected over a pier 22, preferably glued to the back of the sensitive plate and capable of having its tension-adjusted by rotatable peg 23 or by other suitable means commonly employed tor tensioning wires of musical instruments.

By the use of one or more such wires, the

flexibility and absorptive power of the individual plates may be decreased and their reflecting power correspondingly increased by increasing the tension of the backing wires 20. In this way the energies of the different sets of re-radiated waves may be separately and co-relatively adjusted to produce the best acousticalresults.

The modified arrangement shown in Figure 2 will be readily understood after the above description of Figure l. Tn Figure 2 the first reflector 12 is vertical, the second reflector 13" is horizontal. The third reflector 14/ is at an angle of 45 degrees and top and bottom reflectors 17' and 18 are at equal opposite angles of 293?; degrees. 7

The primary waves from the source are directed through pipe 11 to impinge on 1,477 ,libtid reflector 12', at an angle of t5 degrees, as in Figure 1, but in the present case, the first reflector being vertical, pipe 11 delivers the waves at a rearward angle of 45 degrees. In the present case, the sound being derived through a vertical pipe, the pipe is bent to the required angle but it will be understood that the direction from which the waves are derived and whether the pipe is straight or bent is not so important as the direction in which thewaves are projected therefrom at the lower end.

The waves impinging on reflector 12' at b are reflected to point a on reflector 13, thence to reflector 17,thence horizontally along lines 6, f. Thus the main beam has three reflections as in Figure 1, but only 2 tor-.14 is projected at a downward angleot 45 degrees along the lines m-o and impingtill tilt

ing on reflector 18' is projected horizontally along lines 0-'n.

Thus in F igure 2, all three sets of re'radiation waves from the three sonorous reflectors are projected parallel with each other and with the main beam;

Tn both forms of the-projector,it will be understood that the side walls thereof may be transversely plane or curved and longitudinally parallel or diverging as may be desired. They may be either thick enough to be non-vibratory or they may be sensitive sonorous plates.

Tt will be understood that in both forms ct projector, the angles, positions and sizes of the various reflectors may be varied within considerable limits and the parallelism of Mid Milt

the different sets of emitted waves may be ment, or, reflector 1a, Figure 2, being on cited to vibration bnly by secondary waves, 1

re-radiated from sensitive reflector 13, reflector 14* maybe solid. It will be understood, however, that sensitive reflectors at 1 3, Figure 1, wd at it", Figure 2, are out con siderable advantage, both with respect to outgoing waves and reflex waves due to partial reflections occuring at the mouth of' the projector.

In this connection, it should be noted more explicitly with respect to the reflex waves traveling back from the mouth, of the projector in the well known manner characteristic of air column resonance phenomena, that the sonorous reflectors 14 in Figure 1 and 12 Figure 2, are virtually bottoms of the projector mouth pieces 17, 18.and 17, 18'. Hence these reflectors are in position for the reflex wave to impinge thereon at right angles and be again reflected back toward the mouth of the horn, thus actively promoting the longitudinal reflection and re-reflection upon which air column resonance depends.

Figure 2 is peculiar in the further particular that reflex waves traveling back along lines 1 and impinging on reflector 14' are reflected downward so that they impinge vertically upon plate 13 at j-j, whence they are re-reflected vertically from j to k and from 72 to Z, thus the effective acoustical length of the air column from the mouth of the projector to 14, thence to 13' is almost the same as the air column length from the mouth of the projector to 12. The effective air column length will be prefer ably a foot or more, eighteen inches or two feet being even better. The more pronounced the air column resonance, the more important that its fundamental be lower than the phonographic frequencies, if distortion is to be avoided.

As to all of the diagrams, it will be un-' derstood that while the different sets of beams are propagated in the directions in dicated by the arrows, all beams diffuse laterally wherever they are not traveling parallel along a guiding wall and the diffusion wave front being propagated along radiating lines, the wave fronts, that is the layers of alternate condensation and raritication are expanding spheres. These spherical front waves overlap and become more and more parallel the further they travel away from the source. Hence in projectors which emit the various sets of sound waves in approximate parallelism, the overlapping by diffusion will be very complete in a very short distance from the mouth of the projector. Hence, to the hearer, even a short distance in front of the projector, there are no detectable beams of different strengths, the effect being that a single beam of amplified strength and improved quality. Figure 3 illustratespne of the many possible modifications within the spirit of my invention. In this figure, the sound conduit 11, reflector 12' and reflector 13 may be identical with Figure 2 in size, shape and angular arrangement, but the top of the projector instead of being made with the sensitive reflector 14 at 45 degrees and the reflector 17 at 22% degrees has a single plane wall or roof l7 arranged at the 22% degree angle. WVith this modification, all the angles of reflection for the main beam remain precisely as before and the main beam is therefore emitted horizontally as before. The reradiation from plate 12 of course comes out horizontally as before. In case of the reradiation from plate 13, however, the impingement at the top of the projector is at a 62% degree angle instead of the former angle of 45 degrees, consequently it is reflected at a downward angle of 45 degrees and, impinging on plate 18 at the 22% degree angle comes out horizontally as before, but at the bottom instead of top of the projector.

Either or both the walls 17 and 17*, like the walls 17', 18' of Figure 2 or 17 and 18 of Figure 1, may be made of a plate and rigid frame construction similar to the sensitive plates 12, 13 and 14. In such case, however, the plate element will preferably be made somewhat stiffer, either by increased thickness or by the increased number and tension of the backingwires,-thus making them better reflectors and less absorbent of the energy of impinging waves. At the same time they will afford a desired sonorous quality which will be particularly useful in connection with backward traveling reflex waves characteristic of air column resonance.

It will be understood that in the foregoing description and in the following claims the terms up, down, horizontal, vertical, etc., are used for convenience in describing the angular relations of the several parts; that the angular relation thus defined has no particular significance in connection with the terrestrial horizon or a plumb l ne; and that in general, horizontal should be taken as meaning the direction in which it is desired that the waves be em tted; that vertical be taken as meaning perpendicular to the direction of the emission and as in' the plane perpendicular to the successive reflectors which of course corresponds to the plane of the paper in the accompanying drawings. Hence, except in so far as clearly indicated by the context, the above terms should be taken as having the above special meanings. In other words, it is an obvious material fact that any of the projectors shown may be bodily turned or rotated as a whole, up, down, or sidewise through all possible angles permitted by the three dimensions of space without in anymanner modifying the relative arrangement or functioning of the projector as a whole.

I claim:

1. A sound projector having divergent walls affording an air column to be traversed by sound waves, and having opposite .walls by sound waves, and having a pluralit formed as a plurality of cooperating reflectors, one of said reflectors being a sensitive sonorous plate located, at approximately right angles to the path of reflex waves travelling backward from the open mouth of the projecton'in combination with means for propagating sound waves into said projector and into impingement upon said sensitive plate reflector.

2. A sound projector having divergent walls aflording an air column to be traverse? o walls termed as reflectors, one of sai reflectors comprising a rigid non-vibratory frame and a sensitive sonorous plate located, at approximately right angles to the path of reflex waves traveling backward from the open mouth of the projector, in combination with means for propagating sound waves into said projector and into impingement upon said sensitive plate reflector.

3. A sound projector having divergent walls aflording an air column to be traversed by sound waves, and having a plurality of its walls formed and arranged as successively acting reflectors, one of said reflectors being a sensitive sonorous plate located, at approximately right angles to the path of reflex waves traveling backward from the open mouth of the projector, in combination with means for propagating sound waves into said projector in a direction to cause high angle reflect-ion from said sensitive plate reflector,

l. A sound projector having divergent walls aflording an air column to be traversed by sound waves, and having opposite sides formed as a plurality of cooperating reflectors, one of said reflectors being a sensitive sonorous plate located, approximately right angles to the path of reflex waves travelling backward from the open mouth of the projector, in combination with means for propagating sound waves into said projector in such direction that such waves are propagated into impingement at a high angle upon said sensitive plate reflector and are thereby reflected toward the open mouth of the projector" 5. A sound conduit in combination with a tubular projector, of I greater length than wi th to aflord an air column to he trayerse by the sound waves and donned with not less than two sound reflecting surfaces, one of which is a sensitive sonorous plate,

narrate said reflecting surfaces being arranged in cooperative relatlon so that sound waves from the sound conduit implnge upon said sensitive plate and both vthe reflected waves and Ire-radiated waves due to sympathetic vibration of the reflector are emitted from are emitted from the mouth of said pro-.

jector in approximate parallelism.

7. A sound conduit in combination with a projector having opposite sides formed as a plurality of cooperating reflectors, said reflectors including a sensitive sonorous plate arranged at approximately l5 degrees to the axis of the sound conduit, a second sonorous plate at approximately right angles to said flrst mentioned plate, in the path of the reflection therefrom, and at least one other reflector for advancing and bringing into approximate parallelism, the primary sound waves trom the conduit and the reradiatedwaves from the sensitive plate reflectors;

8. A sound conduit in combination with a projector, having opposite sides formed as a. plurality of cooperating reflectors, said reflectors including a sensitive sonorous plate arranged at approximately 45 degrees to the axis of the sound conduit, a second sonorous plate at approximately right angles to said vflrst mentioned plate, in the path of the reflection therefrom, and a third sensitive sonorous plate in cooperative relation with said second plate at an angle of approximately d5 degrees to both said first and second plates, and at least one other reflector for advancing and bringing into approximate parallelism the primary sound waves from the conduit and the re -radiated waves from the sensitive plate reflectors.

Signed at New Yorlr city, in the county of New York and State ol- New Yorlt, this 18th day of dune, l). 1919.

' EL /VQQD GrRlSSlN till 

